Photodiodes embedded within electronic textiles

A novel photodiode-embedded yarn has been presented and characterized for the first time, offering new possibilities for applications including monitoring body vital signs (including heart rate, blood oxygen and skin temperature) and environmental conditions (light, humidity and ultraviolet radiation). To create an E-Textile integrated with electronic devices that is comfortable, conformal, aesthetically pleasing and washable, electronic components are best integrated within the structure of a textile fabric in yarn form. The device is first encapsulated within a protective clear resin micro-pod before being covered in a fibrous sheath. The resin micro-pod and covering fibres have a significant effect on the nature of light received by the photoactive region of the device. This work characterised the effects of both encapsulating photodiodes within resin micro-pods and covering the micro-pod with a fibrous sheath on the opto-electronic parameters. A theoretical model is presented to provide an estimate for these effects and validated experimentally using two photodiode types and a range of different resin micro-pods. This knowledge may have wider applications to other devices with small-scale opto-electronic components. Wash tests confirmed that the yarns could survive multiple machine wash and drying cycles without deterioration in performance

Generación de imágenes sintéticas optimizadas para representaciones masivas de apariencia

La generación de imágenes fotorrealistas es una de las principales disciplinas de la Informática Gráfica que más repercusión tiene hoy en día. Conseguir estas imágenes es un proceso complicado y pesado que requiere simular el transporte que realiza la luz por la escena. Para conseguir una simulación físicamente correcta hay que utilizar un algoritmo adecuado para recorra todos los caminos posibles que realiza la luz y modelos para representar la apariencia de los objetos que forman la escena. Los modelos que definen las propiedades de apariencia suelen estar representados por funciones n-dimensionales que pueden depender de modelos heurísticos o pueden ser datos tabulados provenientes de capturas o simulaciones. Estas funciones describen como interacciona la luz con el material y debido a la dimensionalidad de estas, tabuladas pueden requerir un alto espacio en memoria. Además, cuando los datos están tabulados, la producción de una imagen es muy costosa y ralentiza el ya de por si lento proceso de renderizar una imagen. En este proyecto, con el objetivo de acelerar la convergencia de generación de imágenes sintéticas que requieren de datos tabulados, se propone una adaptación del algoritmo Expectation-Maximization para aproximar de forma eficiente y eficaz datos físicos de la apariencia de los materiales. Generando un Gaussian Mixture Model que adapta la función tabulada mediante la suma de un conjunto de Gaussianas. Permitiendo así, realizar Importance Sampling, una técnica de muestreo que concentra los cálculos en las partes con más contribución a la imagen final, reduciendo el tiempo que necesario para obtener resultados similares

A Microfacet‐based Hair Scattering Model

The development of scattering models and rendering algorithms for human hair remains an important area of research in computer graphics. Virtually all available models for scattering off hair or fur fibers are based on separable lobes, which bring practical advantages in importance sampling, but do not represent physically-plausible microgeometry. In this paper, we contribute the first microfacet-based hair scattering model. Based on a rough cylinder geometry with tilted cuticle scales, our far-field model is non-separable by nature, yet allows accurate importance sampling. Additional benefits include support for elliptical hair cross-sections and an analytical solution for the reflected lobe using the GGX distribution. We show that our model captures glint-like forward scattering features in the R lobe that have been observed before but not properly explained

A Radiative Transfer Framework for Spatially-Correlated Materials

We introduce a non-exponential radiative framework that takes into account the local spatial correlation of scattering particles in a medium. Most previous works in graphics have ignored this, assuming uncorrelated media with a uniform, random local distribution of particles. However, positive and negative correlation lead to slower- and faster-than-exponential attenuation respectively, which cannot be predicted by the Beer-Lambert law. As our results show, this has a major effect on extinction, and thus appearance. From recent advances in neutron transport, we first introduce our Extended Generalized Boltzmann Equation, and develop a general framework for light transport in correlated media. We lift the limitations of the original formulation, including an analysis of the boundary conditions, and present a model suitable for computer graphics, based on optical properties of the media and statistical distributions of scatterers. In addition, we present an analytic expression for transmittance in the case of positive correlation, and show how to incorporate it efficiently into a Monte Carlo renderer. We show results with a wide range of both positive and negative correlation, and demonstrate the differences compared to classic light transport

BxDF material acquisition, representation, and rendering for VR and design

Photorealistic and physically-based rendering of real-world environments with high fidelity materials is important to a range of applications, including special effects, architectural modelling, cultural heritage, computer games, automotive design, and virtual reality (VR). Our perception of the world depends on lighting and surface material characteristics, which determine how the light is reflected, scattered, and absorbed. In order to reproduce appearance, we must therefore understand all the ways objects interact with light, and the acquisition and representation of materials has thus been an important part of computer graphics from early days. Nevertheless, no material model nor acquisition setup is without limitations in terms of the variety of materials represented, and different approaches vary widely in terms of compatibility and ease of use. In this course, we describe the state of the art in material appearance acquisition and modelling, ranging from mathematical BSDFs to data-driven capture and representation of anisotropic materials, and volumetric/thread models for patterned fabrics. We further address the problem of material appearance constancy across different rendering platforms. We present two case studies in architectural and interior design. The first study demonstrates Yulio, a new platform for the creation, delivery, and visualization of acquired material models and reverse engineered cloth models in immersive VR experiences. The second study shows an end-to-end process of capture and data-driven BSDF representation using the physically-based Radiance system for lighting simulation and rendering

The influence of the properties of school uniforms on children with sensory overreactivity

Dissertation (MConsumer Science: Clothing Retail Management)--University of Pretoria, 2021.Many children experience a low threshold towards sensory input and as a result, may experience sensory overreactivity (hypersensitivity) to touch, smell, taste, and intolerance for certain material textures (Cheng & Boggett-Carsjens, 2005; Dunn, 1997; Güçlü, Tanidir, Mukaddes & Ünal, 2007). The nervous system responds with “fight’’ (e.g., tantrums) or ‘flight’’ (e.g., withdrawal) reactions when a child experiences sensory discomfort and irritation (Cheng & Boggett-Carsjens, 2005; Karthikeyan, 2017). Children between the ages of 6-13 years spend approximately five days per week and six to nine hours a day wearing a school uniform which provides a constant sensory input to their body (Dąbrowska, Rotaru, Derler, Spano, Camenzind, Annaheim, Stämpfli, Schmid & Rossi, 2016). The impact of constant discomfort and distraction could be detrimental to a child’s education, social participation, play and activities of daily living. While treatment with an occupational therapist surrounding the effects of Sensory Integration Dysfunction is feasible, it is rather important to address the barriers in the child’s environment that may be the root of the discomfort. It is, therefore, imperative to determine which elements of their school uniforms may cause discomfort and irritation, and subsequently implement measures of adaptation. This study used an exploratory mixed-method to approach this problem. The initial qualitative phase included focus group interviews and, the second quantitative phase consisted of an online self-administered questionnaire. The garment elements explored included three main categories namely textiles (fibre content and fabrication), design (necklines and collars, sleeve and sleeve finishes, waistline finishes, closures, wearing ease, and decorative trimmings) and construction (seam type, seam class and type of labelling). It was important to include both parents of children with sensory overreactivity and qualified occupational therapists in phase 1 and solely parents in phase 2. Due to the explorative nature of the study, convenience sampling, purposive sampling, snowball sampling, and quota sampling was employed in gathering 10 participants for the virtual focus group discussions and 106 respondents for the online questionnaire. The data collected in the qualitative phase (phase 1) was implemented in the development of the measuring instrument used in the quantitative phase (phase 2). Data analysis in phase 1 consisted of content analysis and in phase 2, only descriptive statistics due to the exploratory nature of this study. The findings of this study indicate that school uniforms indeed contribute to sensory overreactivity which may influence children’s quality of life detrimentally. Most influential garment elements include fibre content, rough textures, seam types, collars, long-sleeved garments, embroidery, and labelling. Adaptation guidelines were developed for parents of children with sensory overreactivity, which may also be utilised by occupational therapists. In addition, guidelines for schools, retailers offering school clothing, and manufacturers of school garments were also developed. This study provides a vast contribution to new knowledge which may be used to enhance the lives of children with sensory overreactivity, as well as parents, occupational therapists and teachers who work with children with sensitivities. It may furthermore benefit sensory scientists, researchers in the field of textiles and clothing and consumer scientists.Consumer ScienceMConsumer Science: Clothing Retail ManagementUnrestricte

The influence of the properties of school uniforms on children with sensory overreactivity

Dissertation (MConsumer Science (Clothing Retail Management)--University of Pretoria, 2021.Many children experience a low threshold towards sensory input and as a result, may experience sensory overreactivity (hypersensitivity) to touch, smell, taste, and intolerance for certain material textures (Cheng & Boggett-Carsjens, 2005; Dunn, 1997; Güçlü, Tanidir, Mukaddes & Ünal, 2007). The nervous system responds with “fight’’ (e.g., tantrums) or ‘flight’’ (e.g., withdrawal) reactions when a child experiences sensory discomfort and irritation (Cheng & Boggett-Carsjens, 2005; Karthikeyan, 2017). Children between the ages of 6-13 years spend approximately five days per week and six to nine hours a day wearing a school uniform which provides a constant sensory input to their body (Dąbrowska, Rotaru, Derler, Spano, Camenzind, Annaheim, Stämpfli, Schmid & Rossi, 2016). The impact of constant discomfort and distraction could be detrimental to a child’s education, social participation, play and activities of daily living. While treatment with an occupational therapist surrounding the effects of Sensory Integration Dysfunction is feasible, it is rather important to address the barriers in the child’s environment that may be the root of the discomfort. It is, therefore, imperative to determine which elements of their school uniforms may cause discomfort and irritation, and subsequently implement measures of adaptation. This study used an exploratory mixed-method to approach this problem. The initial qualitative phase included focus group interviews and, the second quantitative phase consisted of an online self-administered questionnaire. The garment elements explored included three main categories namely textiles (fibre content and fabrication), design (necklines and collars, sleeve and sleeve finishes, waistline finishes, closures, wearing ease, and decorative trimmings) and construction (seam type, seam class and type of labelling). It was important to include both parents of children with sensory overreactivity and qualified occupational therapists in phase 1 and solely parents in phase 2. Due to the explorative nature of the study, convenience sampling, purposive sampling, snowball sampling, and quota sampling was employed in gathering 10 participants for the virtual focus group discussions and 106 respondents for the online questionnaire. The data collected in the qualitative phase (phase 1) was implemented in the development of the measuring instrument used in the quantitative phase (phase 2). Data analysis in phase 1 consisted of content analysis and in phase 2, only descriptive statistics due to the exploratory nature of this study. The findings of this study indicate that school uniforms indeed contribute to sensory overreactivity which may influence children’s quality of life detrimentally. Most influential garment elements include fibre content, rough textures, seam types, collars, long-sleeved garments, embroidery, and labelling. Adaptation guidelines were developed for parents of children with sensory overreactivity, which may also be utilised by occupational therapists. In addition, guidelines for schools, retailers offering school clothing, and manufacturers of school garments were also developed. This study provides a vast contribution to new knowledge which may be used to enhance the lives of children with sensory overreactivity, as well as parents, occupational therapists and teachers who work with children with sensitivities. It may furthermore benefit sensory scientists, researchers in the field of textiles and clothing and consumer scientists.National Research Foundation of South Africa (Grant number 129842)Consumer ScienceMConsumer Science (Clothing Retail Management)Unrestricte

Development of solar energy harvesting textiles

The Achilles heel of many wearable and electronic textile (E-textile) devices is their power requirement, which has been a major hurdle in the adoption of E-textiles. To keep these devices continuously powered without frequent recharging or bulky energy storage devices, many have proposed integrating energy harvesting capability into clothing. Solar energy harvesting has been one of the most investigated avenues for this due to the abundance of solar energy and maturity of photovoltaic technologies. This research investigated a novel approach for realising solar energy harvesting with textiles by embedding miniature solar cells (SCs) within the fibres of a yarn, thus delivering a robust and consumer-friendly solution for powering wearable and mobile devices. SCs were first soldered onto fine copper wires and encapsulated inside of resin micro-pods, before being covered by a fibrous sheath, to realise solar cell embedded yarns (solar-E-yarns) that can be readily converted into fabrics with conventional fabric manufacturing processes such as weaving and knitting. Preliminary investigations conducted using miniature photodiode embedded E-yarns laid the foundation for embedding photovoltaic devices within yarns. A mathematical model was also formulated to characterise the performance of photovoltaic devices embedded in yarns and was experimentally validated using photodiodes to evaluate the effects of the resin micro-pod on photovoltaic response. Subsequently solar-E-yarns were fabricated using silicon SCs. The photovoltaic response of these solar-E-yarns were studied at each stage of the E-yarn fabrication process and under a range of test conditions including different light intensities, incident light angles, ambient temperatures and humidity levels. Solar-E-yarn performance could be further enhanced by impregnating the photoactive sides of the yarns with an optically clear resin, as well as by using bifacial SCs. A series of fit-for-purpose tests including wash durability tests were conducted on the solar-E-yarns which revealed that the solar-E-yarn embedded fabrics could undergo domestic laundering and maintained ~90% of the original power output after 15 machine wash cycles, which was vastly superior to other solutions proposed in the literature. To demonstrate the energy harvesting capability, prototype demonstrators were created by weaving solar-E-yarns. A solar fabric demonstrator with ~25cm2 active area generated up to ~2.15 mW/cm2 under one sun illumination and maintained both the feel and aesthetics of a normal textile. The fabric demonstrator was capable of charging various electronic storage and powering low power mobile devices. The research has generated a wealth of knowledge on the fabrication, performance and the utility of the solution for regular clothing applications. These attributes will enable these solar fabrics to feature in future wearable electronics and electronic textiles to provide a continuous supply of power, without having to compromise on comfort, aesthetics or wash durability